Ferroelectric liquid crystal color filter surrounded by a heat fusible resin

ABSTRACT

Surface Stability Ferroelectric Liquid Crystal Device having color filters assembled therein avoids generation of alignment defect ocurring in the initial alignment control step by providing space of 0-5 microns between adjacent color filters.

This application is a division of application Ser. No. 08/352,756, filedDec. 5, 1994, which is a division of application Ser. No. 08/238,345,filed May 5, 1994, now U.S. Pat. No. 5,398,126, issued Mar. 14, 1995which is, in turn a continuation of application Ser. No. 07/806,099,filed Dec. 11, 1991, now abandoned, which is, in turn, a division ofapplication Ser. No. 07/416,034, filed Oct. 2, 1989, now U.S. Pat. No.5,101,289, issued Mar. 31, 1992, which is, in turn, a division ofapplication Ser. No. 07/090,703, filed Aug. 28, 1987, now U.S. Pat. No.4,917,471, issued Aug. 17, 1990.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a ferroelectric liquid crystal device such asa liquid crystal display device or a liquid crystal-optical shutterarray, etc., more particularly to a ferroelectric liquid crystal devicehaving a color filter improved in display and driving characteristics byobtaining a liquid crystal phase of uniform mono-domain withoutalignment defect through improvement of the initial alignment state ofliquid crystal molecules.

2. Related Background Art

Liquid crystal devices known in the art may be, for example, those usingtwisted nematic crystal as disclosed in M. Schadt and W. Helfrich,"Applied Physics Letters", vol. 18, No. 4 (published on Feb. 15, 1971),p. 127-128, "Voltage Dependent Optical Activity of a Twisted-NematicLiquid Crystal". The TN liquid crystal, which involves the problem ofgenerating crosstalk during time divisional driving by use of a matrixelectrode structure with increased picture element density, has beenlimited in number of picture elements.

Also, a display device of the system in which switching elements withthin film-transistors are connected with the respective picture elementsand each picture element is subjected to switching has been known, butthe step of forming thin film transistors on a substrate is extremelycomplicated and furthermore there is the problem that a display devicewith a large area can be prepared with difficulty.

As the device solving these problems, Clark et al. proposed aferroelectric liquid crystal device in U.S. Pat. No. 4,367,924.

This ferroelectric liquid crystal device is generally called SurfaceStability Ferroelectric Liquid Crystal (SSFCC), and is set at asufficiently thin film thickness (e.g., 1 to 2 μm) in order to unwindthe spiral structure inherently possessed by the chiral smectic liquidcrystal. According to Unexamined Japanese Patent Publication No.147232/1986 of Tsuboyama, it has been clarified that when there is astepped difference of 1000 Å or more within the substrate plane used inthe cell forming SSFLC, an alignment defect portion will be generatedaround a stepped portion.

Whereas, for applying the aforementioned ferroelectric liquid crystaldevice to color display, it may be conceivable to arrange a color filterwithin the cell.

In general, a color filter is a structure of a group of color filterunits (each being one R, G or B filter) of red color (R), green color(G) and blue color (B) arranged in a stripe or mosaic shape. Since eachcolor filter unit is formed of a resin film colored into R, G or B,there occurred a stepped difference of about 2000 Å to 1 μm within thesubstrate plane when such color filters were arranged within the cell.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a liquid crystal deviceimproved in generation of the alignment defect which is attributable tothe stepped difference within the substrate plane caused by arrangementof color filters within the cell.

More specifically, the present invention has the specific features in aliquid crystal device which has minimized the influence onto alignmentstability of the ferroelectric liquid crystal by the stepped differencecaused by arrangement of color filters within the cell, namely:

firstly in a liquid crystal device comprising:

(a) a pair of transparent electrodes having a plurality of confrontingportions formed therebetween;

(b) a pair of substrates supporting each of said pair of transparentelectrodes;

(c) a group of color filters comprising a plurality of color filtersarranged on the innerside of at least one of the above pair ofsubstrates and arranged at positions corresponding to each of saidplurality of confronting portions, provided that the relationship of0≦α≦5 is satisfied where α(μm) is the interval of the color filterbetween the adjacent confronting portions; and

(d) a ferroelectric liquid crystal arranged between said pair ofsubstrates;

secondly in a liquid crystal device comprising:

(a) a pair of transparent electrodes having a plurality of confrontingportions formed therebetween;

(b) a pair of substrates supporting each of said pair of transparentelectrodes;

(c) a group of color filters comprising a plurality of color filtersarranged on the innerside of at least one of the above pair ofsubstrates and arranged at positions corresponding to each of saidplurality of confronting portions, provided that the color filterspositioned at at least two confronting portions of the pluralconfronting portions are different in film thickness and therelationship of X≦(1/10).d₀ is satisfied where d₀ is the interval (μm)between the above pair of substrates and X(μm) is the maximum filmthickness-difference; and

(d) a ferroelectric liquid crystal arranged between said pair ofsubstrates;

thirdly in a liquid crystal device comprising:

(a) a pair of transparent electrodes having a confronting portion formedtherebetween;

(b) a pair of substrates supporting each of said pair of transparentelectrodes;

(c) color filters arranged on the innerside of at least one of the abovepair of substrates and arranged at positions corresponding to saidconfronting portion;

(d) resin films arranged adjacent to said color filters, the resin filmshaving a first resin film and a second resin film formed with a resinsolution having a viscosity higher than the resin solution used whensaid first resin film is formed; and

(e) a ferroelectric liquid crystal arranged between said pair ofsubstrates;

fourthly in a liquid crystal device comprising:

(a) a pair of transparent electrodes forming a plurality of confrontingportions;

(b) a pair of substrates supporting each of said pair of transparentelectrodes;

(c) a group of color filters comprising a plurality of color filtersarranged on the innerside of at least one of the above pair ofsubstrates and arranged at positions corresponding to each of saidplurality of confronting portions, said color filters being formed intrapezoidal shapes, provided that the relationships of 0°<θ<90° and0<W≦d/tan θ are satisfied where d(μm) is the thickness of said colorfilter, θ(degree) is the sectional taper angle between the lower bottomof the color filter and the diagonal side thereof and W(μm) is theoverlapping width between the adjacent color filters; and

(d) a ferroelectric liquid crystal arranged between said pair ofsubstrates;

fifthly in a liquid crystal device comprising:

(a) a pair of transparent electrodes forming a plurality of confrontingportions;

(b) a pair of substrates supporting each of said pair of transparentelectrodes;

(c) a group of color filters comprising a plurality of color filtersarranged on the innerside of at least one of the above pair ofsubstrates and arranged at positions corresponding to each of saidplurality of confronting portions;

(d) a heat-fusible resin film arranged at the gap between the adjacentcolor filters; and

(e) a ferroelectric liquid crystal arranged between said pair ofsubstrates; and

sixthly in a liquid crystal device comprising:

(a) a pair of transparent electrodes forming a plurality of confrontingportions;

(b) a pair of substrates supporting each of said pair of transparentelectrodes;

(c) a group of color filters comprising a plurality of color filtersarranged on the innerside of at least one of the above pair ofsubstrates and arranged at positions corresponding to each of saidplurality of confronting portions, provided that the relationship of0≦l/d≦5 is satisfied where l(μm) is the interval between the colorfilters of the adjacent confronting portions and d(μm) is the filmthickness of said color filter; and

(d) a ferroelectric liquid crystal arranged between said pair ofsubstrates.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1, 2, 3, 4A, 4B, 5 and 6 are sectional views of the ferroelectricliquid crystal devices of the present invention.

FIG. 7 and FIG. 8 are perspective views showing schematically theferroelectric liquid crystals used in the present invention.

FIGS. 9A-9F, 10A-10G, 11A-11F, 12A-12G, 13A-13F and 14A-14F aresectional views showing the production processes of the color filtersubstrates used in the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS

The present inventors have found, as a result of experiments, that noalignment defect is generated by setting the interval α(μm) between thefilter units of the color filter built in the cell at 5 μm or less,regardless of the above stepped difference. Particularly, it has beenfound that by setting the interval α(μm) between the filter units at 5μm or less upon formation of the initial alignment state in thetemperature drop process when the ferroelectric liquid crystal istransferred from the isotropic phase (high temperature state) to theliquid crystal phase (low temperature state), no alignment defect isgenerated.

Referring to the drawings, the present invention is explained below.

FIG. 1 is a sectional view showing the basic constitution of theferroelectric liquid crystal device according to the present invention.In FIG. 1, the ferroelectric liquid crystal device 11 has substrates 12and 13 using transparent plates such as glass plate or plastic plate,and has a ferroelectric liquid crystal 14 sandwiched therebetween. Therespective substrates 12 and 13 have the respective transparentelectrodes 15 and 16 in patterns of stripes for forming matrix electrodestructures arranged thereon, and on the transparent electrodes areformed alignment control films 17 and 18. The respective color units ofred (R), green (G) and blue (B) are formed of materials with coloredmaterial concentrations previously set so as to give desired spectralcharacteristics when their film thickness are equal to each other. Onthe other hand, for effecting further flattening, a light interceptinglayer 10 is formed in the recess between the respective color units, ifnecessary, and further a protective film or a flattening layer 19 isformed thereon.

In the substrates according to the above constitution, by setting thefilm thickness of the color filters at substantially the same andsuppressing the interval between the filter units at 5 μm or less, thestepped difference due to the recess is corrected, and therefore thesubstrate surface can be maintained substantially flat, even iftransparent electrodes and alignment control films may be successivelyformed on the filter units.

In the present invention, by flattening as described above, the steppeddifference of the color filter substrate can be set at 1000 Å or less,preferably 500 Å or less. If the stepped difference exceeds 1000 Å, inother words, if a non-flattened layer with the intervals between therespective filter units set in the range exceeding 5 μm is used, theliquid crystal device will give rise to an alignment defect in shape ofa blade line as shown above in FIG. 5.

The ferroelectric liquid crystal device of the present invention has thecolor filters of the respective filter units formed with substantiallythe same film thickness and also the interval α(μm) between the colorfilters of the adjacent respective filter units is 0≦α≦5 μm, andtherefore the flatness of the substrate becomes good. As the result,there is no stepped difference at the plane in contact with the liquidcrystal phase, and the liquid crystal phase sandwiched between saidsubstrates with good flatness is gradually cooled in the temperatureprocess transferring from the isotropic phase to the liquid phase,whereby the liquid phase region is gradually expanded to form a liquidcrystal phase of uniform monodomain.

For example, to explain by referring to the above mentioned DOBAMBCexhibiting ferroelectric liquid phase as the liquid phase, when theisotropic phase of DOBAMBC is gradually cooled, phase transition to thesmectic A phase (SmA phase) occurs at about 115° C. At this time, if thesubstrate is subjected to orientation treatment such as rubbing or SiO₂oblique vapor deposition, a monodomain, in which the molecular axes ofthe liquid crystal molecules are parallel to the substrate and arealigned in one direction, is formed. As cooling is further progressed,phase transition to the chiral smectic C phase (SmC* phase) occurs at aspecific temperature between about 90° and 75° C., depending on thethickness of the liquid crystal layer. Also, when the thickness of theliquid crystal layer is set at about 2 μm or lower, the spiral of theSmC* phase is loosened to exhibit bistability.

According to a preferred example of the present invention, it isdesirable that the film thicknesses of the color filter units may differfor each of R, G and B, particularly with the maximum thickness beingset for B color filter units, the minimum thickness for R color filterunits, and the intermediate thickness for G color filter units. At thistime the maximum film thickness difference X (μm) corresponds to thefilm thickness difference between the B color filter units and the Rcolor filter units, and generation of alignment defect can be avoided byhaving color filters built in within the cell, the filters being set atthe relationship of X≦(1/10).d₀ where X(μm) is the maximum filmthickness difference and d₀ (μm) is the distance between a pair of thesubstrates.

FIG. 2 shows a sectional view of the ferroelectric liquid crystal cellas described above, the same symbols as in FIG. 1 representing the samemembers. In the ferroelectric liquid crystal device shown in FIG. 2, therelationship of X≦(1/10).d₀ preferably (1/20).d₀ is satisfied whereX(μm) is the maximum film thickness difference of the color filter units(R, G, B) and d₀ (μm) is the interval of a pair of substrates 12 and 13.Also, as is clarified in Examples as described below, if X is set toexceed (1/10).d₀ alignment defect will occur from the stepped portion,and the ferroelectric liquid crystal at such alignment defect portionwas found to give rise to switching defect (exhibiting no normal drivingcharacteristics).

The film thicknesses dR, dG, dB of the color filter units, R, G and Bused in the ferroelectric liquid cell shown in FIG. 2 may be set eachwithin the range of 0.5 μm to 1.5 μm, particularly preferably atdB>dG>dR.

In another preferable example of the present invention, generation ofthe above mentioned alignment defect can be prevented by improving theprotective film arranged between the color filters and the transparentelectrodes.

FIG. 3 is a sectional view of such ferroelectric liquid crystal cell, inwhich the same symbols as in FIG. 1 represent the same members.

In FIG. 3, the ferroelectric liquid crystal device 11 has substrates 12and 13 using transparent plates such as glass plate or plastic plate,and has a ferroelectric liquid crystal 14 sandwiched therebetween. Therespective substrates 12 and 13 have the respective transparentelectrodes 15 and 16 in patterns of stripes for forming matrix electrodestructures arranged thereon, and on the transparent electrodes areformed alignment control films 17 and 18. The respective color units ofred (R), green (G) and blue (B) are formed with film thicknesses setdepending on the desired spectral characteristics with steppeddifferences to some extent.

On the other hand, if desired, a light intercepting layer 10 is formedin the gap between the respective color units. Also, on the colorfilters, a first transparent resin film 31, which is formed of a lowerviscosity resin and is a flattened layer flattening the steppeddifference between the picture elements, and a second transparent resinfilm 32, which is formed of a higher viscosity resin and is theflattened layer and the protective layer for the color filters, aresuccessively laminated.

In the substrate according to the above constitution, since the steppeddifference due to film thicknesses of color filters and the recessbetween the filter units is corrected, the substrate plane can bemaintained substantially flat.

The color filter to be used in the present invention is not particularlylimited, provided that it has characteristics such as environmentalresistance for the conditions in the steps for formation of theferroelectric liquid crystal device and also has desired durability. Itmay be prepared by forming a pigment and a layer containing it into apattern. The layer thickness may be determined depending on the desiredspectral characteristics. It may be generally about 0.5 to about 5 μm,preferably about 0.5 to about 1.5 μm, with the layer thickness of eachcolor being preferably as small as possible.

Further, in some cases, in order to improve the display characteristicsand make the stepped difference in the gap between the respective colorfilter units, a light intercepting layer can be more effectively formedby depositing a metallic thin film having light intercepting abilitysuch as chromium, aluminum, etc. according to the vapor depositionmethod or by applying a light intercepting resin film containing amaterial having light intercepting ability such as carbon black,composite oxide black pigment, metal powder, etc. dispersed in aphotosensitive polyamino type resin according to the coating method.

The first transparent resin film 31 of the present invention is formedprimarily for the purpose of flattening the stepped difference on thesubstrate formed after color filter formation. Accordingly, a resin madeto have a lower viscosity is used, and generally a viscosity of 50 cps(centipoise) or less/(under room temperature), preferably a viscosity of20 to 50 cps is desirable. The color filter surface is coated withliquids, which are controlled to lower viscosity, of organic resin suchas polyamide type, polyimide type, polyurethane type, acrylic type,polycarbonate type and silicone type, etc. or solutions of thephotosensitive resins thereof according to the coating method such asspin coating, roll coating, dipping, etc., and then are subjected to thephotolithographic processing, forming the resin film. Its film thicknessmay be the thickness necessary for filling the unit gap portion of thecolor filter, and it is preferable that the thickness is set to be equalto or slightly thicker than the thickness of the thickest unit.

The second transparent resin film 32 is formed on the layer which hasbeen substantially flattened with the first transparent resin film 31,and is formed for the purpose of flattening further the steppeddifference owing to the color filters and primarily protecting the colorfilters. Accordingly, with a resin material with increased resincomponent, with a viscosity generally exceeding 50 cps(centipoise)/(under room temperature), preferably controlled within therange of about 100 cps to about 1200 cps, for example, with organicresin liquids such as polyamide type, polyimide type, polyurethane type,acrylic type, polycarbonate type and silicone type, etc. or solutions ofthe photosensitive resins, the film 31 are coated according to thecoating method such as spin coating, roll coating, dipping, etc., andthen are subjected to the photolithographic steps, forming the resinfilm 32.

As to the resin material for forming the second resin film 32, it may besame as a material of the first transparent resin film 31 or different,and any desired material can be selected from those having resistance tothe respective environments in the cell forming steps of theferroelectric liquid crystal device and having desired reliability, etc.Its layer thickness may be set as desired from the viewpoints asmentioned above. The layer is generally formed with a thickness of about0.5 to about 5 μm, preferably about 0.5 to about 1.0 μm.

According to another preferable example of the present invention, thecolor filter unit is formed in a trapezoidal shape, and generation ofalignment defect as described above can be avoided by having a group ofcolor filters built in the cell, said group having the relationships of0°<θ<90° and 0<w≦d/tan θ where d(μm) is the film thickness of said colorfilter unit, θ(degree) is the sectional tapered angle between the bottomand the diagonal side of the color filter unit and w(μm) is theoverlapping width between the adjacent color filter units.

FIG. 4A is a sectional view of the ferroelectric liquid crystal cell asdescribed above, with the same symbols as in FIG. 1 representing thesame members.

In the cell shown in FIG. 4, the respective color filter units of R(red), G (green) and B (blue) are formed in trapezoidal shapes, with thecolorant concentrations being previously set to give desired spectralcharacteristics in equal film thicknesses, the tapered angles beingformed by control of exposure, having overlapped portions at theadjacent units and a part of the diagonal sides thereof.

More specifically, when d(μm) is the film thickness of the color filterunit formed in trapezoidal shape as shown in FIG. 4B, θ(degree) is thesectional tapered angle between the bottom and the diagonal side of thecolor filter unit and w(μm) is the overlapping width between thediagonal sides of the adjacent color filter units,

(1) the range of the sectional tapered angle of one unit is set at0<θ<90°, and

(2) the range of the overlapping width between the adjacent units is setat 0<w≦d/tan θ. If necessary, a protective film or flattening film 19 isformed on the color filter layer.

In the substrate 12 with the above constitution, since the steppeddifference due to the film thicknesses of color filters and the recessbetween units is corrected, the substrate plane can be maintainedsubstantially flat even when transparent electrode 15 and alignmentcontrol film 17 may be successively formed on the color filters.

According to another example of the present invention, by arranging aheat-fusible resin film at the gap between the adjacent color filterunits of the group of color filter units, generation of the abovementioned alignment defect can be avoided.

FIG. 5 is a sectional view of the ferroelectric liquid crystal cell asmentioned above, with the same symbols as in FIG. 1 representing thesame members. In FIG. 5, a heat-fusible resin film 51 is provided in aform such that the film binds the respective color filter units of R, Gand B. The heat-fusible resin film 51 can be provided by coating atleast one substrate with a heat-fusible resin and forming color filterson said heat-fusible resin film 51, or by coating the substrate havingcolor filters formed thereon with a heat-fusible resin and then fillingthe color filter unit gap with the heat-fusible resin film 51 by meansof heating or heating under pressurization.

As the heat-fusible resin for forming the heat-fusible resin film 51used in the present invention, there may be employed polyvinyl acetate,ethylene-vinyl acetate copolymer, polyvinyl chloride, vinylchloride-vinyl acetate copolymer, polyamide, phenoxy resin, ethylcelulose, polyisobutylene, polyester, terpene resin, rosin andderivatives thereof, petroleum resin, etc., either singly or as amixture. Desirably, it is effective to use a resin with hightransparency.

As the method for forming the heat-fusible resin film 51, the firstmethod forms first a resin layer with a film thickness of about 0.5 toabout 5 μm on a substrate according to the coating method such as spincoating, roll coating, dipping, etc. by use of a heat-fusible resinsolution. Next, after formation of the color filter layer with patternformation having the above constitution on said resin layer, the colorfilter pattern is embedded in the molten resin by the heating treatmentunder the melting temperature of the heat-fusible resin, or the hotpress treatment in parallel to said color filter substrate surface, orby use of air blow, etc., simultaneously with flattening of the surfacelayer, and then are subjected to fixation by cooling to normaltemperature.

On the other hand, the second method comprises forming a color filterpattern on the substrate, then forming the heat-fusible resin film 51having the same film thickness according to the same coating method asin the above method, subsequently embedding the molten resin in the gapsof the color filter pattern by heat treatment, hot press treatment orair blow, etc. similarly as the above method, simultaneously byflattening the surface layer and then fixing the resulting resin bycooling to normal temperature.

In some cases, for improving the display characteristics, a lightintercepting layer can formed at the gaps of the respective color filterunits by depositing a metal film having light intercepting ability suchas chromium, aluminum, etc. according to the vapor deposition method orby applying a light intercepting resin layer containing a materialhaving light intercepting ability such as carbon black, black pigment ofcomposite oxides, metal powder, etc. according to the coating method.

Further, when it is required to further increase adhesiveness betweenthe heat-fusible resin or the color filter layer and the base substrate,it is more effective to precoat the substrate thin with a silanecoupling agent before formation of the heat-fusible resin or the colorfilter layer, or to use the heat-fusible resin or the color filter layerinto which a small amount of a silane coupling agent, etc. is previouslyadded.

For the purpose of protecting the color filter layer and theheat-fusible film 51 from various environmental conditions and furtherflattening the surface, an organic resin such as polyamide, polyimide,polyurethane, polycarbonate, silicone, etc. or an inorganic film such asSi₃ N₄, SiO₂, SiO, Al₂ O₃, Ta₂ O₃, etc. can be provided as theprotective film or the flattening film generally having the thicknessrange of about 0.5 to about 5 μm by the coating method such as spincoating, forming the resin film 32, the vapor deposition method.

According to another preferable example of the present invention,generation of the above mentioned alignment defect can be avoided by Useof a group of color filter units satisfying the relationship of 0≦l/d≦5where l(μm) is the interval between the adjacent color filter units inthe group of color filter units and d(μm) is the film thickness of thecolor filter unit.

FIG. 6 shows a sectional view of the ferroelectric liquid crystal cellas mentioned above, with the same symbols as in FIG. 1 representing thesame members. On the substrate 12 shown in FIG. 6 are formed the colorfilter units B, G and R with the same film thickness, and simultaneouslythe interval l(μm) between the color filter units is set at 5-fold orless relative to the film thickness d(μm) of the color filter unit.

The color filter suitable for the present invention may be a filteraccording to the system capable of setting the film thicknesses of therespective color filter units at substantially same thickness.Particularly the system as described below, according to which a finepattern can be formed by a simple production process and a color filterexcellent in mechanical characteristics as well as variouscharacteristics such as heat resistance, light resistance, solventresistance, etc. can be afforded, is preferred.

The optimum color filter for the present invention is formed byrepeating the photolithographic step of a colored resin comprising acolorant material dispersed in an aromatic polyamide resin or polyimideresin having photosensitive groups in the molecule.

More particularly, the aromatic polyamide resin or polyimide resinhaving photosensitive groups in the molecule for forming the coloredresin layer possessed by the color filter may be preferably one whichcan give a cured film at 200° C. or lower, for example, which is capableof forming a cured film by heating of about 150° C. for 30 minutes,particularly one having no specific light absorption characteristic inthe visible wavelength region (400-700 nm) (one having lighttransmittance of about 90% or more). From this standpoint, an aromaticpolyamide resin is preferred.

Also, as the group having photosensitivity in the present invention,aromatic chains having a photosensitive unsaturated hydrocarbon group asshown below may be employed.

(1) Benzoic acid esters: ##STR1## (wherein R¹ representsCHX═CY--COO--Z--, X represents --H or --C₆ H₅, Y represents --H or--CH₃, Z represents - or an ethyl group or a glycidyl group);

(2) Benzyl acrylates: ##STR2## (wherein Y represents --H or CH₃); (3)Diphenyl ethers: ##STR3## (wherein R₂ represents a group containing atleast one of CHX═CY--CONH--, CH₂ ═CY--COO--(CH₂)₂ --OCO-- or CH₂═CY--COO--CH₂ --, X and Y represent the same groups as above);

(4) Chalcons and other compound chains: ##STR4## (wherein R₃ representsH--, an alkyl group or an alkoxy group); ##STR5## and so on.

Specific examples of the aromatic polyamide resin and polyimide resinshaving these groups in the molecules may include "Risocoat PA-1000"(trade name, produced by Ube Kosan K. K.), "Risocoat PI-400" (trade nameproduced by Ube Kosan K. K.).

Generally, few photosensitive resins used in the photolithographic stepare excellent in mechanical characteristics and durability such as heatresistance, light resistance, solvent resistance, although there in suchcharacteristics may be different depending on the chemical structure. Incontrast, the above photosensitive polyamino type resin of the presentinvention is a resin excellent in these durabilities, also in chemicalstructure, and the durability of the color filter formed by use of thesealso becomes very good. Particularly, excellent performances will beexhibited for heat resistance during sputter formation of a transparentelectroconductive film on the color filter and for breakage of the colorfilter owing to inner spacer during assembling of the liquid crystaldevice, such heat resistance and breakage being significant for thecolor filter for ferroelectric liquid crystal device.

The colorant material for forming the colored resin layer possessed bythe color filter in the present invention is not particularly limited inorganic pigments, inorganic pigments, dyes, etc., provided thatdesirable spectral characteristics can be obtained. In this case, eachmaterial can be used singly or as a mixture of some of these. However,when a dye is used, the performance of the color filter is governed bythe durability of the dye itself, whereas when the above resin system isused, a color filter with better performance than conventionally dyedcolor filters are obtained. Accordingly, in view of the colorcharacteristics and various performances of the color filter, an organicpigment is the most preferred as the colorant material.

As the organic pigment, there may be employed typically azo typepigments such as soluble azo type, insoluble azo type, condensed azotype, etc., also phthalocyanine type pigments, and indigo type,anthraquinone type, perylene type, perynone type, dioxazine type,quinacridone type, isoindolinone type, phthalone type,methine-azomethine type, other condensed polycyclic pigments containingmetal complex type or mixtures of some of these.

In the present invention, the colored resin to be used for formation ofthe colored resin layer may be prepared by formulating each of the abovecolorant materials having desired spectral characteristics under thesame film thickness for each color into the above photosensitivepolyamino type resin solution at a proportion of about 10 to about 70wt. %, dispersing sufficiently the colorant materials by use ofsupersonic, three-rolls, ball mill, sand mill, etc., and preferably thenremoving the colorant material of great particle size through a filterof 1 μm or less.

The colored resin layer possessed by the color filter in the presentinvention is formed by coating the above colored resin onto a substrateaccording to a coating device such as spinner, roll coater, etc. andthen forming it into a pattern shape according to the photolithographicstep, and its layer thickness may be determined depending on the desiredspectral characteristics. The colored layer generally has the samethickness for each color of about 0.5 to about 3.0 μm, preferably about0.5 to about 1.5 μm.

When it is required to further increase adhesion between the coloredresin layer and the substrate of the base, it is further effective tocoat previously the substrate thin with a silane coupling agent, etc.before pattern formation of the colored resin, or to form the colorfilter by use of a material having a small amount of a silane couplingagent, etc. previously added into the colored resin.

The colored resin layer possessed by the color filter of the presentinvention is constituted of a material having itself sufficientdurability. Particularly, for protection of the colored resin layer fromvarious environmental conditions or flattening of the color filtersurface, an organic resin such as polyamide, polyimide, polyurethane,polycarbonate, silicone type, etc. or an inorganic film such as Si₃ N₄,SiO₂, SiO, Al₂ O₃, Ta₂ O₃, etc. can be provided as the protective filmor the flattening film according to the coating method such as spincoating, roll coating, etc., or according to the vapor depositionmethod.

In this case, the color filter surface becomes a shape with less steppeddifference, which is suitable for removing the alignment defect of theferroelectric liquid crystal device as intended by the presentinvention.

The film thickness of the protective film 19 can determine the filmthickness of the ferroelectric liquid crystal 14 and therefore may varydepending on the kind of the liquid crystal material and the responsespeed required, etc., and it is generally set in the range of 0.2 μm to20 μm, preferably 0.5 μm to 10 μm.

Also, in some cases, for improving display characteristics and makingthe gap stepped difference between the respective units smaller, lightintercepting layers can be formed, correspondingly between therespective units, by depositing a metal thin film having lightintercepting ability such as chromium, aluminum, etc. according to thedeposition method or by applying a light intercepting resin layercontaining a material having light intercepting ability such as carbonblack, black pigment of composite oxides, metal powder, etc. dispersedin a photosensitive polyamide or polyimide resin according to thecoating method.

The material for the alignment control film to be used in the presentinvention may be selected from, for example, resins such as polyvinylalcohol, polyimide, polyamideimide, polyester, polycarbonate, polyvinylacetal, polyvinyl chloride, polyvinyl acetate, polyamide, polystyrene,cellulose resin, melamine resin, urea resin, acrylic resin, etc., orphotosensitive polyimide, photosensitive polyamide, cyclic rubber typephotoresist, phenol novolac type photoresist or electron beamphotoresist (polymethyl methacrylate, epoxidized 1,4-polybutadiene,etc.) and so on. The thickness of the alignment control film 7 is setgenerally in the range of 10 Å to 1 μm, preferably 100 Å to 3000 Å,depending on the film thickness of the ferroelectric liquid crystal.

As the liquid crystal material to be used in the present invention,particularly suitable ones are liquid crystals having bistability andferroelectric characteristics. Specifically, liquid crystals of thechiral smectic phase (SmC*), the H phase (SmH*), the I phase (SmI*), theJ phase (SmJ*), the K phase (SmK*), the G phase (SmG*) or the F phase(SmF*) can be used.

Details of the ferroelectric liquid crystals are described in "LEJOURNAL DE PHYSIQUE LETERS", 1975, 36, (L-69), "Ferroelectric LiquidCrystals"; "Applied Physics Letters", 1980, 36 (11), Submicro SecondBistable Electrooptic Switching in Liquid Crystals; "Solid Physics",1981, 16 (141), "Liquid Crystal", U.S. Pat. Nos. 4,561,726, 4,589,996,4,596,667, 4,613,209, 4,614,609, 4,639,089, and the ferroelectric liquidcrystals disclosed in these references can be used in the presentinvention.

Specific examples of ferroelectric liquid crystal may include

desiloxybenzylidene-p'-amino-2-methylbutylcinnamate (DOBAMBC),

hexyloxybenzylidene-p'-amino-2-chloropropylcinnamate (HOBACPC),

4-o-(2-methyl)-butylresorcilidene-4'-octylaniline (MBRAS).

When the device is constituted by use of these materials, since thetemperature state is maintained so that the liquid crystal compound maybecome the chiral smectic phase, the device can be supported by, e.g., ablock in which heater is embedded, if necessary.

FIG. 7 illustrates schematically an example of cell for description ofactuation of the ferroelectric liquid crystal. 71a and 71b aresubstrates (glass plates) covered with transparent electrode comprisinga thin film of In₂ O₃, SnO₂ or ITO (Indium Tin Oxide), etc., andtherebetween is sealed a liquid crystal of the SmC* phase or the SmH*phase with a plurality of liquid crystal molecular layers 72 beingaligned perpendicularly to the glass surface. The line 73 indicated bybold line-represents the liquid crystal molecule, and the liquid crystalmolecule 73 has dipole moment (P⊥) 74 in the direction orthogonal to themolecule. When a voltage of a certain threshold value or higher isapplied between the electrodes on the substrate 71a and 71b, the spiralstructure of the liquid crystal molecule 73 can be loosened to changethe aligned direction of the liquid crystal molecules 73 so that thedipole moment (P⊥) 74 may be all directed to the electrical fielddirection. The liquid crystal molecule 73 has a slender shape,exhibiting refractive index anisotropy in its longer axis direction andshorter axis direction. Therefore, it is readily understood that when,or example, polarizers positioned at the positional relationship ofcrossed Nicols to each other are arranged on upper and lower sides ofthe glass surface, a liquid crystal optical modulating device can varyits optical characteristics according to the polarity of the appliedvoltage.

The liquid crystal cell to be used preferably in the ferroelectricliquid crystal device of the present invention can have a thicknesswhich can be made sufficiently thin (e.g. 10 μ or less). As the liquidcrystal phase becomes thus thinner, the spiral structure of the liquidcrystal molecule will be loosened even when no electrical field isapplied, becoming a non-spiral structure, whereby its dipole moment Paor Pb takes either the state directed upwardly (84a) or downwardly(84b). When an electrical field Ea or Eb with different polarity of acertain threshold value or higher is imparted to such a cell, the dipolemoment will change the direction upwardly 84a or downwardly 84bcorresponding to the electrical field vector of the electrical field Eaor Eb, whereby the liquid crystal molecules will be aligned in eitherone of the first stable state 83a or the second stable state 83b.

There are two advantages as mentioned above brought about by use of suchferroelectric liquid crystal as the optical modulating device. The firstone is the extremely rapid response speed, and the second one is thatthe alignment of liquid crystal molecules has bistability. To explainfurther the second point by referring to, for example, FIG. 8, liquidcrystal molecules will be aligned into the first stable state 83a byapplication of the electrical field Ea, and this state is stable even ifthe electrical field may be turned off. On the other hand, when theelectrical field Eb in the opposite direction is applied, the liquidcrystal molecules will be aligned into the second stable state 83b tochange the direction of molecules, but they also remain under this stateeven when the electrical field may be turned off. Also, as long as theelectrical field Ea does not exceed a certain threshold value, therespective aligned states are still maintained. For such rapid responsespeed and bistability to be realized effectively, the cell should bepreferably as thin as possible.

For the ferroelectric liquid crystal device exhibit desired drivingcharacteristics, the ferroelectric crystal arranged between a pair ofparallel substrates is required to take the molecular alignment statesuch that conversion between the above two stable states may effectivelyoccur irrespectively of the applied state of electrical field. Forexample, for a ferroelectric liquid crystal having the chiral smecticphase, it is required that a region in which the liquid crystal moleculelayer of the chiral smectic phase is arranged vertically to thesubstrate surface, and therefore the liquid crystal molecule axis insubstantially parallel to the substrate surface (monodomain) should beformed. For this purpose, a uniformly aligned monodomain can beeffectively formed with the alignment control films 17 and 18 asdescribed above.

The present invention is described in detail below by referring to thefollowing Examples.

EXAMPLE 1

FIGS. 9A-9F are diagrams of the steps showing the formation steps of thecolor filter units of the three colors R, G and B.

First, on #7059 glass substrate 91 produced by Corning was formed acolored resin layer 92 by coating of a blue colored resin materialcapable of obtaining desired spectral characteristics [the blue coloredresin material being a photosensitive colored resin material prepared bydispersing Heliogen Blue L7080 (trade name, produced by BASF Co., C.I.No. 74160) in PA-1000C (trade name, produced by Ube Kosan K. K., polymercontent=10%, solvent: N-methyl pyrrolidone, pigment:polymer=1:2)]according to spinner coating to a film thickness of 1.5 μm (see FIG.9A).

Next, said colored resin layer 92, after prebaked at 80° C. for 30minutes, was subjected to exposure by use of a high pressure mercurylamp through a photomask 93 corresponding to the pattern shape to beformed (see FIG. 9B).

After exposure, as shown in FIG. 9C, the layer 92 was developed by useof supersonic with an exclusive developer (comprisingN-methyl-2-pyrroidone as the main component) which dissolved only theunexposed portion of the colored resin layer 92 having the photocuredportion 92a, and then the layer 92 was treated with an exclusive rinsesolution (e.g. a rinse solution comprising isopropyl alcohol as the maincomponent), followed by post-baking at 150° C. for 30 minutes, to form ablue pattern colored resin layer 94 having a pattern shape (see FIG.9D).

Subsequently, on the glass substrate having a blue colored patternformed thereon, a green pattern colored resin layer 95 was formed at thepredetermined portion on the substrate with an interval of 5 μm or lessset from the blue colored resin layer in the same manner as describedabove except for using as the second color a green colored resinmaterial [photosensitive colored resin material prepared by dispersingLionol Green 6YK (trade name, produced by Toyo Ink, C.I. No. 74265) inPA-1000 C (trade name, produced by Ube Kosan K. K., polymer content=10%,solvent: N-methyl-2-pyrrolidone, pigment:polymer=1:2)].

Further, on the substrate having thus formed blue and green patternsthereon, a red pattern colored resin layer 96 was formed at thepredetermined portion on the substrate with the respective intervals of5 μm or less set from the blue colored resin layer and the green coloredresin layer in the same manner as described above except for using asthe third color a red colored resin material [photosensitive coloredresin material prepared by dispersing Irgazine Red BPT (trade name,produced by Ciba-Geigy Co., C. I. No. 71127) in PA-1000 C (trade name,produced by Ube Kosan K. K., polymer content=10%, solvent:N-methyl-2-pyrrolidone, pigment:polymer=1:2)], thus obtaining a coloredpattern of the three color stripes of R (red), G (green) and B (blue)(see FIG. 9E).

Next, on the glass substrate having the colored pattern of the threecolors formed thereon, as the light intercepting layer, a lightintercepting layer 97 with a light intercepting pattern was formed inconformity with the gap between the respective units according to amethod similar to that as described above by use of a black coloredresin material [photosensitive colored resin material prepared bydispersing Carbon Black (C.I. No. 77266) in PA-1000 C (polymercontent=10%, pigment:polymer=1:4)]. By this, the gap α(μm) between therespective units could be made to fall within the range of 0≦α≦5 μm.

On the color filter pattern thus obtained, as the protective film or theflattening film 98, a film the same transparent resin material as usedfor the colored resin material [PA-1000 C (trade name, produced by UbeKosan K. K., polymer content=10%, solvent: N-methyl-2-pyrrolidone)] wasformed by the spinner coating method to a film thickness of about 0.5 μm(see FIG. 9F).

As described above, a flat color filter substrate could be formed.

Next, as shown in FIG. 1, ITO film was formed according to thesputtering method to a thickness of 500 Å to form transparent electrode15. The electrode was coated with a polyimide forming solution ("PIQ"produced by Hitachi Kasei Kogyo) by a spinner rotating at 3000 rpm,followed by heating at 150° C. for 30 minutes to form a polyimidecoating of 2000 Å as the alignment control film 17. Then, rubbingtreatment was applied on the polyimide coating surface.

The color filter substrate thus formed and confronting substrate 13 wereadhered together to be assembled into a cell, and "CS-1014" (trade name)produced by Chisso K. K. which is a ferroelectric liquid crystal wasinjected therein and sealed to obtain a liquid crystal device. When theliquid crystal device was observed by means of a polarizing microscopeof crossed Nicols, it was confirmed that no orientation defect wasformed in the internal liquid crystal molecules.

As described above, according to the present invention, there is no filmthickness difference in the color filter layer on the substrate, andmoreover the respective filter units are positioned within the intervalα(μm) in the range of 0≦α≦5 μm, and further a light intercepting layer,a protective or flattening layer, if necessary, are provided, whereby ithas become possible to remove even fine stepped differences occurringbetween the respective color filter units, and generation of alignmentdefect can be avoided to provide a ferroelectric liquid crystal devicewhich can exhibit fully the characteristics of a ferroelectric liquidcrystal.

Additionally, according to the present invention, it has become possibleto prepare a color filter portion having a fine pattern having alsoexcellent mechanical strength as well as various excellentcharacteristics such as heat resistance, light resistance, solventresistance, etc. according to simple preparation steps, whereby a colorferroelectric liquid crystal having excellent performances could beprovided.

Next, a cell was prepared according to entirely the same procedure asdescribed above except that the interval α(μm) between the color filterunits was set at 8 μm. As the result, alignment defects around thestepped portions of the color filters could be confirmed.

EXAMPLE 2

First, on #7059 glass substrate 91 produced by Corning was formed acolored resin layer 92 by coating of a blue colored resin materialcapable of obtaining desired spectral characteristics [the blue coloredresin material being a photosensitive colored resin material prepared bydispersing Heliogen Blue L7080 (trade name, produced by BASF Co., C.I.No. 74160) in PA-1000 C (trade name, produced by Ube Kosan K. K.,polymer content=10%, solvent: N-methyl pyrrolidone,pigment:polymer=1:2)] according to spinner coating to a film thicknessof 1.5 μm.

Next, said colored resin layer, after prebaked at 80° C. for 30 minutes,was subjected to exposure by use of a high pressure mercury lamp througha photomask corresponding to the pattern shape to be formed.

After exposure, the colored resin layer was developed by use ofsupersonic with an exclusive developer (comprisingN-methyl-2-pyrrolidone as the main component) which dissolved only theunexposed portion of the colored resin layer having the photocuredportion, and then the colored resin layer was treated with an exclusiverinse solution (e.g. a rinse solution comprising isopropyl alcohol asthe main component), followed by post-baking at 180° C. for 30 minutes,to form a blue pattern colored resin layer having a pattern shape.

Subsequently, on the glass substrate having a blue colored patternformed thereon, a green pattern colored resin layer was formed at thepredetermined portion on the substrate in the same manner as describedabove except for using as the second color a green colored resinmaterial [photosensitive colored resin material prepared by dispersingLionol Green 6YK (trade name, produced by Toyo Ink, C.I. No. 74265) inPA-1000 C (trade name, produced by Ube Kosan K. K., polymer content=10%,solvent: N-methyl-2-pyrrolidone, pigment:polymer=1:2)].

Further, on the substrate having thus formed blue and green patternsthereon, a red pattern colored resin layer was formed at thepredetermined portion on the substrate in the same manner as describedabove except for using as the third color a red colored resin material[photosensitive colored resin material prepared by dispersing IrgazineRed BPT (trade name, produced by Ciba-Geigy Co., C.I. No. 71127) inPA-1000 C (trade name, produced by Ube Kosan K. K. polymer content=10%,solvent: N-methyl-2-pyrrolidone, pigment:polymer=1:2)], thus obtaining acolored pattern of the three color stripes of R (red), G (Green) and B(blue) with the maximum film thickness difference of 0.1 μm.

Next, on the glass substrate having the colored pattern of the threecolors formed thereon, as the light intercepting layer, a lightintercepting layer with a light intercepting pattern was formed inconformity with the gap between the respective units according to thesame method as described above by use of a black colored resin material[photosensitive colored resin material prepared by dispersing CarbonBlack (C.I. No. 77266) in PA-1000 C (polymer content=10%,pigment:polymer=1:4)].

On the color filter pattern thus obtained, as the protective film or theflattening film, a film of the same transparent resin material as usedfor the colored resin material [PA-1000 C (trade name, produced by UbeKosan K. K., polymer content=10%, solvent: N-methyl-2-pyrrolidone)] wasformed by the spinner coating method to a film thickness of about 0.5μm.

As described above, a flat color filter substrate could be formed.

Next, as shown in FIG. 2, ITO film was formed according to thesputtering to a thickness of 500 Å to form transparent electrode 15. Theelectrode was coated with a polyimide forming solution ("PIQ" producedby Hitachi Kasei Kogyo) by a spinner rotating at 3000 rpm, followed byheating at 150° C. for 30 minutes to form a polyimide coating of 2000 Åas the alignment control film 17. Then, rubbing treatment was applied onthe polyimide coating surface.

The color filter substrate thus formed and confronting substrates 13were adhered together to be assembled into a cell, and a ferroelectricliquid crystal was injected therein and sealed to obtain a liquidcrystal device. When the liquid crystal device was observed by apolarizing microscope of crossed Nicols, it was confirmed that noorientation defect was formed in the internal liquid crystal molecules.

Next, a cell was prepared according to entirely the same procedure asdescribed above except that the maximum film thickness difference wasset at 0.3 μm. As the result, alignment defects around the steppeddifference portions of the color filters could be confirmed.

EXAMPLE 3

FIGS. 10A-10G are the diagrams of the steps showing an example of theformation steps of the color units of color filters of the three colorsof R, G and B.

This Example describes about the case by use of a color filter formed byrepeating the photolithographic step of a colored resin comprising acolorant material dispersed in polyamide having photosensitive group inthe molecule, which is the excellent system in which the film thicknessof the respective color units can be made substantially constant bysetting previously the concentration of the colorant materials and finepatterns can be formed by a simple preparation process, and which isfurther excellent in mechanical characteristics and also in variousexcellent characteristics such as heat resistance, light resistance,solvent resistance, etc.

First, on #7059 glass substrate 101 produced by Corning was formed acolored resin layer 102 by coating of a blue colored resin materialcapable of obtaining desired spectral characteristics [the blue coloredmaterial being a photosensitive colored resin material prepared bydispersing Heliogen Blue L7080 (trade name, produced by BASF Co., C.I.No. 74160) in PA-1000 C (trade name, produced by Ube Kosan K. K.,polymer content=10%, solvent: N-methyl pyrrolidone,pigment:polymer=1:2)] according to spinner coasting to a film thicknessof 1.5 μm (see FIG. 10A).

Next, said colored resin layer 102, after prebaked at 80° C. for 30minutes, was subjected to exposure by use of a high pressure mercurylamp through a photomask 103 corresponding to the pattern shape to beformed (see FIG. 10B).

After exposure, as shown in FIG. 10C, the layer 102 was developed by useof supersonic with an exclusive developer (comprisingN-methyl-2-pyrroidone as the main component) which dissolved only theunexposed portion of the colored resin layer 102 having the photocuredportion 102a, and then the layer was treated with an exclusive rinsesolution (e.g. a rinse solution comprising isopropyl alcohol as the maincomponent), followed by post-baking at 150° C. for 30 minutes, to form ablue pattern colored resin layer 104 having a pattern shape (see FIG.10D).

Subsequently, on the glass substrate having a blue colored patternformed thereon, a green pattern colored resin layer 105 was formed atthe predetermined portion on the substrate in the same manner asdescribed above except for using as the second color a green coloredresin material [photosensitive colored resin material prepared bydispersing Lionol Green 6YK (trade name, produced by Toyo Ink, C.I. No.74265) in PA-1000 C (trade name, produced by Ube Kosan K. K., polymercomponent=10%, solvent: N-methyl-2-pyrrolidone, pigment:polymer=1:2)].

Further, on the substrate having thus formed blue and green patternsthereon, a red pattern colored resin layer 106 was formed at thepredetermined portion on the substrate in the same manner as describedabove except for using as the third color a red colored resin material[photosensitive colored resin material prepared by dispersing IrgazineRed BPT (trade name, produced by Ciba-Geigy Co., C.I. No. 71127) inPA-1000 C (trade name, produced by Ube Kosan K. K. polymercomponent=10%, solvent: N-methyl-2-pyrrolidone, pigment:polymer=1:2)],thus obtaining a colored pattern of the three color stripes of R (red),G (green) and B (blue) (see FIG. 10E).

Next, on the glass substrate having the colored pattern of the threecolors formed thereon, as the light intercepting layer, a lightintercepting layer 107 with a light intercepting pattern was formed inconformity with the gap between the respective picture elementsaccording to the same method as described above by use of a blackcolored resin material [photosensitive colored resin material preparedby dispersing Carbon Black (C.I. No. 77266) in PA-1000 C (polymercomponent=10%, pigment:polymer=1:4)].

On the color filter pattern thus obtained, the first transparent resinlayer 108 was formed by applying a photosensitive polyamide resinsolution previously controlled to have a viscosity of 50 cps [PA-1000 C(trade name, produced by Ube Kosan K. K., solvent:N-methyl-2-pyrrolidone)] according to the spinner coating method to afilm thickness of about 0.5 μm (see FIG. 10F).

Prebaking (70° C. for 20 minutes), exposure, developing, rinsing andpost-baking (150° C. for 30 minutes) treatments were conducted to form aflattened layer, and then on said transparent resin layer 108 wasformed, as the second transparent resin layer 109, a film of aphotosensitive polyamide resin solution previously controlled to have aviscosity of 100 cps [PA-1000 C (trade name, produced by Ube Kosan K.K., solvent: N-methyl-2-pyrrolidone)] by the spinner coating method to afilm thickness of about 1 μm (see FIG. 10G).

Prebaking (70° C. for 20 minutes), exposure, developing, rinsing,post-baking (150° C. for 30 minutes) treatments were conducted to form aprotective film.

As described above, a flat color filter substrate could be formed.

Next, as shown in FIG. 3, ITO film was formed according to thesputtering method to a thickness of 500 Å to form transparent electrode15. The electrode was coated with a polyimide forming solution ("PIQ"produced by Hitachi Kasei Kogyo) by a spinner rotating at 3000 rpm,followed by heating at 150° C. for 30 minutes to form a polyimidecoating of 2000 Å as the alignment control film 17. Then, rubbingtreatment was applied on the polyimide coating surface.

The color filter substrate thus formed and confronting substrates 13were adhered together to be assembled into a cell, and a ferroelectricliquid crystal was injected therein and sealed to obtain a liquidcrystal device. When the liquid crystal device was observed by means ofa polarizing microscope of crossed Nicols, it was confirmed that noorientation defect was formed in the internal liquid crystal molecules.

As described above, according to the present invention, even when thereis difference in film thickness of the color filter layers on thesubstrate, by laminating succesively a first transparent resin layerformed of a lower viscosity resin which brings about flattening on saidcolor filter layers and a second transparent resin layer formed of ahigher viscosity resin which brings about flattening and protection, itbecomes possible to remove fine stepped differences in film thicknessdifference occurring between the respective color filter units orstepped difference in the respective unit intervals, whereby generationof alignment defect can be avoided to provide a ferroelectric liquidcrystal device capable of exhibiting fully the characteristics of aferroelectric liquid crystal.

Next, a cell was prepared according to entirely the same procedure asdescribed above except for omitting use of the first transparent resinfilm and the second transparent resin film. As the result, alignmentdefects around the stepped difference portions of the color filterscould be confirmed.

EXAMPLE 4

FIGS. 11A-11G are the diagrams of the steps showing the formation stepsof the color units of the three colors of R, G and B.

First, on #7059 glass substrate 111 produced by Corning was formed acolored resin layer 112 by coating of a blue colored resin materialcapable of obtaining desired spectral characteristics [the blue coloredresin material being a photosensitive colored resin material prepared bydispersing Heliogen Blue L7080 (trade name, produced by BASF Co., C.I.No. 74160) in PA-1000 C (trade name, produced by Ube Kosan K. K.,polymer content=10%, solvent: N-methyl pyrrolidone,pigment:polymer=1:2)] according to spinner coating to a film thicknessof 1.5 μm (see FIG. 11A).

Next, said colored resin layer 112, after prebaked at 80° C. for 30minutes, was subjected to excess exposure by use of a high pressuremercury lamp through a photomask 113 corresponding to the pattern shapeto be formed (see FIG. 11B).

After exposure, as shown in FIG. 11C, the layer 112 was developed by useof supersonic with an exclusive developer (comprisingN-methyl-2-pyrrolidone as the main component) which dissolved only theunexposed portion of the colored resin layer 102 having the photocuredportion 102a, and the layer 112 was treated with an exclusive rinsesolution (e.g. a rinse solution comprising isopropyl alcohol as the maincomponent), followed by post-baking at 150° C. for 30 minutes, to form ablue pattern colored resin layer 114 having a tapered shape (angle=15°)at the end of the trapezoidal shape (see FIG. 11D).

Subsequently, on the glass substrate having a blue colored patternformed thereon, a green pattern colored resin layer 115 was formed,partially overlapping with the blue pattern shape colored resin layer(overlapping width w=5 μm) at the predetermined portion on the substratein the same manner as described above except for using as the secondcolor'a green colored resin material [photosensitive colored resinmaterial prepared by dispersing Lionol Green 6YK (trade name, producedby Toyo Ink, C.I. No. 74265) in PA-1000 C (trade name, produced by UbeKosan K. K., polymer content=10%, solvent: N-methyl-2-pyrrolidone,pigment:polymer=1:2)].

Further, on the substrate having thus formed blue and green patternsthereon, a red pattern colored resin layer 116 was formed, partiallyoverlapping with the blue pattern colored resin layer and the greenpattern colored resin layer (overlapping width w=5 μm) at thepredetermined portion on the substrate in the same manner as describedabove except for using as the third color a red colored resin material[photosensitive colored resin material prepared by dispersing IrgazineRed BPT (trade name, produced by Ciba-Geigy Co., C.I. No. 71127) inPA-1000 C (trade name, produced by Ube Kosan K. K., polymer content=10%,solvent: N-methyl-2-pyrrolidone, pigment:polymer=1:2), thus obtaining acolored pattern of the three color stripes of R (red), G (green) and B(blue) (see FIG. 11E).

Next, on the glass substrate having the colored pattern of the threecolors formed thereon, as the light intercepting layer, a lightintercepting layer 117 with a light intercepting pattern was formed inconformity with the gap between the respective units according to thesame method as described above by use of a black colored resin material[photosensitive colored resin material prepared by dispersing CarbonBlack (C.I. No. 77266) in PA-1000 C (polymer content=10%,pigment:polymer=1:4)].

On the color filter pattern thus obtained, as the protective film orflattening film 118, a film of the same transparent resin material asused for the colored resin material [PA-1000 C (trade name, produced byUbe Kosan K. K., polymer content=10%, solvent: N-methyl-2-pyrrolidone)]was formed by the spinner coating method to a film thickness of about1.0 μm (see FIG. 11F).

As described above, a flat color filter substrate could be formed.

Next, as shown in FIG. 4, ITO film was formed according to thesputtering method to a thickness of 500 Å to form transparent electrode15. The electrode was coated with a polyimide forming solution ("PIQ"produced by Hitachi Kasei Kogyo) by a spinner rotating at 3000 rpm,followed by heating at 150° C. for 30 minutes to form a polyimidecoating of 2000 Å as the alignment control film 17. Then, rubbingtreatment was applied on the polyimide coating surface.

The color filter substrate thus formed and confronting substrate 13 wereadhered together to be assembled into a cell, and a ferroelectric liquidcrystal was injected therein and sealed to obtain a liquid crystaldevice. When the liquid crystal device was observed by a polarizingmicroscope of crossed Nicols, it was confirmed that no orientationdefect was formed in the internal liquid crystal molecules.

As described above, according to the present invention, by setting atapered angle at the range of 0° to 90° to the color filter pictureelements on the substrate and providing overlapping portions between theadjacent units in the range of 0 to [d (film thickness)/tan θ (taperedangle)], the stepped difference in the unit interval can be alleviatedto 1/2 at the maximum as compared with conventional unit pattern, andeven in the case when there is unit deviation caused by alignmentstepped difference during unit formation, the stepped difference causedthereby can be reduced to 1/2 of the conventional case, wherebygeneration of alignment defect can be avoided to provide a ferroelectricliquid crystal device capable of exhibiting fully the characteristics ofa ferroelectric liquid crystal.

EXAMPLE 5

FIGS. 12A-12G are diagrams of steps showing a first formation stepincluding the three color filter layers and a heat-fusible resin layer.

First, on #7059 glass substrate 121 produced by Corning Co., theheat-fusible resin layer 125 was formed by applying a methyl acetatesolution of an ethylene-vinyl acetate copolymer at a layer thickness of1.0 μm by use of a spinner. Then, the layer 125 was coated with apositive-type resist (trade name: OFPR 77, produced by Tokyo Oka) at alayer thickness of 1.0 μm by use of a spinner to provide a resist layer122 (see FIG. 12A). Next, by use of a predetermined pattern mask, theresist layer was exposed to light (see FIG. 12B) and developed with anODUR 1010 series exclusive developer to form a resist pattern 122a forlift-off having a predetermined stripe shape (see FIG. 12C).

Next, the whole surface of the pattern-formed surface of the glasssubstrate 121 was exposed to light, and further unnecessary resistresidue other than the pattern portion was removed from the glasssubstrate 121 by oxygen plasma ashing treatment.

The glass substrate 121 having thus the pattern 122a for lift-off formedthereon was arranged at a predetermined position in a vacuum vapordeposition apparatus, nickel phthalocyanine was placed as the blue dyefor vapor deposition in the molybdenum boat as the vaporization source,and a colored layer 124 was formed by vapor deposition of nickelphthalocyanine to a thickness of 4500 Å on the pattern formed surfacefor lift-off by controlling the vaporization temperature of the formerto 470° C. (see FIG. 12D).

The substrate 121 having the pattern 122a and the colored layer 124formed thereon was dipped for 5 minutes and stirred in an OFPR 77 seriesexclusive developer to remove the colored layer 124a vapor deposited onthe pattern together with the resist pattern, whereby a blue colorstripe filter was prepared (see FIG. 12E).

On the other hand, green and red stripe filters were obtained byrepeating the steps of FIGS. 12A-12E. First, as the green dye for vapordeposition, lead phthalocyanine was vapor-deposited to a thickness of5000 Å to form a green layer.

Next, as the red dye for vapor deposition, anthraquinone wasvapor-deposited to a thickness of 3000 Å to form a red layer.

As described above, color filters of B, G and R could be formed as shownin FIG. 12F.

Next, after the color filters containing the heat-fusible resin layerwere subjected to hot press at about 150° C. to embed the heat-fusibleresin in the gaps between the color filter units, the temperature wasreturned to room temperature to form a layer binding color filters (seeFIG. 12G).

Next, as the protective film 19, a negative resist (ODUR, produced byTokyo Oka) was formed by coating. At this stage, the color filtersubstrate is formed on entirely the same plane.

Next, as shown in FIG. 5, ITO film was formed according to thesputtering method to a thickness of 500 Å to form transparent electrode15. The electrode was coated with a polyimide forming solution ("PIQ"produced by Hitachi Kasei Kogyo) by a spinner rotating at 3000 rpm,followed by heating at 150° C. for 30 minutes to form a polyimidecoating of 2000 Å as the alignment control film 17. Then, rubbingtreatment was applied on the polyimide coating surface.

The color filter substrate thus formed and confronting substrate 13 wereadhered together to be assembled into a cell, and a ferroelectric liquidcrystal was injected therein and sealed to obtain a liquid crystaldevice. When the liquid crystal device was observed by a polarizingmicroscope of crossed Nicols, it was confirmed that no orientationdefect was formed in the internal liquid crystal molecules.

EXAMPLE 6

FIGS. 13A-13G are the diagrams of the steps showing the second stepincluding the color filter layers of the three colors of R, G and B andthe heat-fusible resin layer.

First, on #7059 glass substrate 131 produced by Corning was formed acolored resin layer 132 by coating of a blue colored resin materialcapable of obtaining desired spectral characteristics [the blue coloredresin material being a photosensitive colored resin material prepared bydispersing Heliogen Blue L7080 (trade name, produced by BASF Co., C.I.No. 74160) in PA-1000 C (trade name, produced by Ube Kosan K. K.,polymer content=10%, solvent: N-methyl pyrrolidone,pigment:polymer=1:2)] according to spinner coating to a film thicknessof 1.5 μm (see FIG. 13A).

Next, said colored resin layer 132, after prebaked at 80° C. for 30minutes, was subjected to exposure by use of a high pressure mercurylamp through a photomask 133 corresponding to the pattern shape to beformed (see FIG. 13B).

After exposure, as shown in FIG. 13C, the layer 132 was developed by useof supersonic with an exclusive developer comprisingN-methyl-2-pyrrolidone as the main component) which dissolved only theunexposed portion of the colored resin layer 132 having the photocuredportion 132a, and then the layer 132 was treated with an exclusive rinsesolution (e.g. a rinse solution comprising isopropyl alcohol as the maincomponent), followed by post-baking at 150° C. for 30 minutes, to form ablue pattern colored resin layer 134 having a pattern shape (see FIG.13D).

Subsequently, on the glass substrate having a blue colored patternformed thereon, a green pattern colored resin layer 135 was formed atthe predetermined position on the substrate in the same manner asdescribed above except for using as the second color a green coloredresin material [photosensitive colored resin material prepared bydispersing Lionol Green 6YK (trade name, produced by Toyo Ink, C.I. No.74265) in PA-1000 C (trade name, produced by Ube Kosan K. K., polymercontent=10%, solvent: N-methyl-2-pyrrolidone, pigment:polymer=1:2)].

Further, on the substrate having thus formed blue and green patternsthereon, a red pattern colored resin layer 136 was formed at thepredetermined position on the substrate in the same manner as describedabove except for using as the third color a red colored resin material[photosensitive colored resin material prepared by dispersing IrgazinRed BPT (trade name, produced by Ciba-Geigy Co., C.I. No. 71127) inPA-1000 C (trade name, produced by Ube Kosan K. K., polymer content=10%,solvent: N-methyl-2-pyrrolidone, pigment:polymer=1:2), thus obtaining acolored pattern of the three color stripes of R (red), G (green) and B(blue) (see FIG. 13E)].

Next, the color filter obtained was coated with a methyl acetatesolution of an ethylene-vinyl acetate copolymer resin at a layerthickness of 1.5 μm by use of a spinner, and the coated product wassubjected to hot press at about 150° C. to embed the heat-fusible resin137 in the gaps between the color filter units, followed by cooling tonormal temperature to form a layer binding color filters (see FIG. 13F).

On the color filter pattern thus obtained, as the protective film orflattening film 138, a film of the same transparent resin material asused for the colored resin material [PA-1000 C (trade name, produced byUbe Kosan K. K., polymer content=10%, solvent: N-methyl-2-pyrrolidone)]was formed by the spinner coating method to a film thickness of about0.5 μm (see FIG. 13F)].

As described above, a color filter substrate made on the same planecould be formed.

Next, as shown in FIG. 5, ITO film was formed according to thesputtering method to a thickness of 500 Å to form transparent electrode15. The electrode was coated with a polyimide forming solution ("PIQ"produced by Hitachi Kasei Kogyo) by a spinner rotating at 3000 rpm,followed by heating at 150° C. for 30 minutes to form a polyimidecoating of 2000 Å as the alignment control film 17. Then, rubbingtreatment was applied on the polyimide coating surface.

The color filter substrate thus formed and confronting substrates 13were adhered together to be assembled into a cell, and a ferroelectricliquid crystal was injected therein and sealed to obtain a liquidcrystal device. When the liquid crystal device was observed by apolarizing microscope of crossed Nicols, it was confirmed that noorientation defect was formed in the internal liquid crystal molecules.

As described above, according to the present invention, since thedifference in film thickness between the color filter layers and thegaps between the color filter units are filled with a heat-fusibleresin, great stepped difference does not occur, and further by providinga protective or flattening film as desired, it becomes also possible toremove fine stepped difference occurring between the respective units ofcolor filters, whereby generation of alignment defect could be avoidedto provide a ferroelectric liquid crystal device capable of exhibitingfully the characteristics of a ferroelectric liquid crystal.

Next, a cell was prepared in the same manner as described above exceptfor omitting use of the heat-fusible resin film. As the result,alignment defects could be confirmed at the color filter steppeddifference portions.

EXAMPLE 7

FIGS. 14A-14G are the diagrams of the steps showing the formation stepsof the color units of the three colors of R, G and B.

First, on #7059 glass substrate 141 was formed a colored resin layer 142by coating of a blue colored resin material capable of obtaining desiredspectral characteristics [the blue colored resin material being aphotosensitive colored resin material prepared by dispersing HeliogenBlue L7080 (trade name, produced by BASF Co., C.I. No. 74160) in PA1000C (trade name, produced by Ube Kosan K. K., polymer content=10%,solvent: N-methyl pyrrolidone, pigment:polymer=1:2)] according tospinner coating to a film thickness of d μm (see FIG. 14A).

Next, said colored resin layer 142, after prebaked at 70° C. for 30minutes, was subjected to exposure by use of a high pressure mercurylamp through a photomask 143 corresponding to the pattern shape to beformed (see FIG. 14B).

After exposure, as shown in FIG. 14C, the layer 142 was developed by useof supersonic with an exclusive developer (the developer comprisingN-methyl-2-pyrrolidone as the main component) which dissolved only theunexposed portion of the colored resin layer 142 having the photocuredportion 142a, and then the layer 142 was treated with an exclusive rinsesolution (e.g. a rinse solution comprising isopropyl alcohol as the maincomponent), followed by post-baking at 200° C. for 30 minutes, to form ablue pattern colored resin layer 144 having a pattern shape (see FIG.14D).

Subsequently, on the glass substrate having a blue colored patternformed thereon, a green pattern colored resin layer 145 was formed witha unit interval from the blue colored pattern as a measured value l(μm)on the substrate in the same manner as described above by using as thesecond color a green colored resin material [photosensitive coloredresin material prepared by dispersing Lionol Green 6YK (trade name,produced by Toyo Ink, C.I. No. 74265) in PA-1000 C (trade name, producedby Ube Kosan K. K., polymer content=10%, solvent:N-methyl-2-pyrrolidone, pigment:polymer=1:2)].

Further, on the substrate having thus formed blue and green patternsthereon, a red pattern colored resin layer 136 was formed with a unitinterval from the blue and the green colored patterns as a measuredvalue l(μm) at the predetermined position on the substrate in the samemanner as described above except for using as the third color a redcolored resin material [photosensitive colored resin material preparedby dispersing Irgazin Red BPT (trade name, produced by Ciba-Geigy Co.,C.I. No. 71127) in PA-1000 C (trade name, produced by Ube Kosan K. K.,polymer content=10%, solvent: N-methyl-2-pyrrolidone,pigment:polymer=1:2)], thus obtaining a colored pattern of the threecolor stripes of R (red), G (green) and B (blue) (see FIG. 14E).

Next, on the glass substrate having the colored pattern of the threecolors formed thereon, as the light intercepting layer, a lightintercepting layer 147 with a light intercepting pattern was formed inconformity with the gap between the respective units according to aprocedure similarly to that as described above by use of a black coloredresin material [photosensitive colored resin material prepared bydispersing Carbon Black (C.I. No. 77266) in PA-1000 C (polymercontent=10%, pigment:polymer=1:4)].

On the color filter pattern thus obtained, as the protective film orflattening film 148, a film of the same transparent resin material asused for the colored resin material [PA-1000 C (trade name, produced byUbe Kosan K. K., polymer content=10%, solvent: N-methyl-2-pyrrolidone)]was formed by the spinner coating method to a film thickness of about0.5 μm (see FIG. 14F).

Next, as shown in FIG. 6, ITO film was formed according to thesputtering method to a thickness of 500 Å to form transparent electrode15. The electrode was coated with a polyimide forming solution ("PIQ"produced by Hitachi Kasei Kogyo) by a spinner rotating at 3000 rpm,followed by heating at 150° C. for 30 minutes to form a polyimidecoating of 2000 Å as the alignment control film 17. Then, rubbingtreatment was applied on the polyimide coating surface.

The color filter substrate thus formed and confronting substrate 13 wereadhered together to be assembled into a cell, and "CS-1014" (trade name)produced by Chisso K. K. which is a ferroelectric liquid crystal wasinjected therein and sealed to obtain a liquid crystal device. When theliquid crystal device was observed by a polarizing microscope of crossedNicols, and the extent of alignment defect of the internal liquidcrystal molecules was evaluated.

In the above method, the film thickness d (μm) of color filter and thedistance l(μm) between the respective units of color filters were variedfor evaluation of alignment defects to obtain the results shown in Table1.

                  TABLE 1                                                         ______________________________________                                               Test 1 Test 2  Test 3   Test 4 Test 5                                  ______________________________________                                        d (μm)                                                                              0.9      1.0     1.5    1.5    2.1                                   l (μm)                                                                              5.2      4.7     5.0    9.0    11.0                                  l/d      5.8      4.7     3.3    6.0    5.2                                   Alignment                                                                              Δ  ◯                                                                         ◯                                                                        X      Δ                               defect state                                                                  ______________________________________                                         Note)                                                                         (1) The values of d and l are those measured.                                 (2) Evaluation of alignment defect state: The symbol ◯ means      the state free substantially from any problem. The symbol Δ means       the state that slight defects are recognized. The symbol X means the stat     that remarkable defects are recognized.                                  

As described above, according to the present invention, by setting theintervals between the respective units of the color filters on thesubstrate at 5-fold or less of the film thickness, it has becomepossible to reduce remarkably the alignment defect caused by the steppeddifference between the units.

Also, by providing a light intercepting layer, a protective orflattening layer on the color filter as desired, it has become possibleto alleviate sufficiently the stepped difference occurring between therespective units of the color filter, whereby generation of alignmentdefect could be avoided to provide a ferroelectric liquid crystal devicecapable of exhibiting fully the characteristics of a ferroelectricliquid crystal.

We claim:
 1. A liquid crystal device comprising:(a) a pair oftransparent electrodes having a plurality of confronting portions formedtherebetween; (b) a pair of substrates, one of said pair substratessupporting each of said pair of transparent electrodes; (c) a pluralityof color filters arranged on the innerside of at least one of the abovepair of substrates and arranged at positions corresponding to each ofsaid plurality of confronting portions; (d) a heat-fusible resin filmarranged at the gaps between adjacent color filters, and wherein theheat-fusible resin is above and below the color filters; and (e) aferroelectric liquid crystal arranged between said pair of substrates.2. A liquid crystal device according to claim 1, wherein said colorfilters are arranged between one of said pair of substrates and one ofsaid pair of transparent electrodes formed on said one of said pair ofsubstrates.
 3. A liquid crystal device according to claim 1, wherein aprotective film is arrived between said color filters and said pair oftransparent electrodes.
 4. A liquid crystal device according to claim 1,wherein said heat-fusible resin film is formed of at least one resinselected from the group consisting of polyvinyl acetate, ethylene-vinylacetate copolymer, polyvinyl chloride, vinyl chloride-vinyl acetatecopolymer, polyamide, phenoxy resin, ethyl cellulose, polyisobutylene,polyester, terpene resin, rosin and petroleum resin.
 5. A liquid crystaldevice according to claim 1, wherein said color filters are formedaccording to the photolithographic step of a color resin comprising acolorant material dispersed in a low-temperature-curing polyamino typeresin having a photosensitive group in the molecule.
 6. A liquid crystaldevice according to claim 5, wherein said polyamino type resin is anaromatic polyamide resin or polyimide resin having photosensitive groupin the molecule and is capable of giving a cured film at 200° C. orlower.
 7. A liquid crystal device according to claim 1, wherein aprotective film is provided between said color filters and said pair ofelectrodes.
 8. A liquid crystal device according to claim 1, wherein analignment control film is provided for said ferroelectric liquidcrystal.
 9. A liquid crystal device according to claim 8, wherein amonoaxial alignment treatment axis is imparted to said alignment controlfilm.
 10. A liquid crystal device according to claim 9, wherein saidmonoaxial alignment treatment axis is a rubbing treated axis.
 11. Aliquid crystal device according to claim 1, wherein the film thicknessof each color filter is set in the range of from 0.5 μm to 5 μm.
 12. Aliquid crystal device according to claim 1, wherein said color filterexhibits blue, green or red color per each color filter.
 13. A liquidcrystal device according to claim 1, wherein the formation of the spiralstructure of the ferroelectric liquid crystal is suppressed.
 14. Aliquid crystal device according to claim 13, wherein said color filtersare arranged between the substrates and the transparent electrodes. 15.A liquid crystal device according to claim 13, wherein a protective filmis arranged between said color filters and the transparent electrodes.